The present invention relates to a composition and method of making same for use in a size composition for treating glass fibers during or after forming with an aqueous size composition which prepares the glass fibers for bonding to polyolefin resin in the reinforcement of specific polyolefin materials.
Glass fibers have many uses one of which is for reinforcement material in the form of continuous strands, chopped strands, mats, roving or woven cloth for polyolefins. The glass fiber reinforced polyolefins have better dimensional stability, tensile strength, flexural modulus, flexural strength, impact resistance and creep resistance than unreinforced polyolefin material.
The glass fibers for use as reinforcement material are made by drawing at a high rate of speed a multitude of molten glass streams that flow from small openings in a bushing. The fibers are treated with a size composition that performs several functions. It protects the fibers during gathering into a strand or strands and during further processing. It also has the capability to couple or to adhere the glass fibers with the polyolefin material in which the glass fibers are to be used as reinforcement. In addition, the size composition makes the surface of the glass fibers compatible with the polyolefin material. The size composition performs these functions by containing the following components usually in an aqueous dispersion or an emulsion: a glass fiber lubricant, a coupling agent, and a film forming synthetic resinous binder. After the glass fibers are treated with the size composition, they are gathered together and wrapped on a tube or spool by a winder that usually also provides the pulling force to draw the fibers to produce a forming package. The glass fibers are removed from the forming package to produce the fiber glass products used to reinforce polyolefin material.
The resinous binder or finishing material that is a component of the size composition used to treat glass fibers to be used to reinforce polyolefin material is usually an aqueous pololefin emulsion. This emulsion can be a polypropylene emulsion, a polypropylene-polyethylene emulsion, or carboxylated polypropylene emulsion, or carboxylated polypropylene-polyethylene emulsion. Illustrative examples of such emulsions include the following U.S. Pat. Nos. 3,655,353; 3,849,148; 3,882,068; 3,814,715 (Nalley et al). As taught in U.S. Pat. No. 3,655,353 (Nalley et al) the emulsion is prepared by melting polypropylene (and polyethylene when used) and adding suitable emulsifying agents with stirring and then adding water until the water and oil emulsion invert to an oil in water emulsion. The emulsions are made to contain about 20 to 40 percent by weight of solids (non-aqueous ingredients) based upon the weight of emulsion. Suitable emulsifying agents include Triton X-100, Igepal C0-630 and Tergitol. The polypropylene employed in the size has an average molecular weight in the range of about 5,300 to 7,300 and a ring and ball softening point of 150.degree. to 175.degree. C., and a density of 0.85 to 1 gram per cubic centimeter, and a penetration hardness (100 grams/5 seconds/22.degree. C. [72.degree. F.]) in tenths of a millimeter of 0.01 maximum. Several polypropylene or polypropylene/polyethylene emulsions are commercially available, such as RL 3974 and Abraze-ade emulsions both of which are marketed by Proctor Chemical Corporation. These emulsions are based on the use of the amorphous polypropylene, since the amorphous polypropylene can be easily converted into an aqueous emulsion.
Polymers of the alpha-olefin, monomer type such as polypropylene, exist in several stereosiomeric polymeric forms. When the polymer is in the plainer zig-zag form there are three possible configurational arrangements for the substitute groups. The isotactic form is where the substituents appear always on the same side of the main chain and the syndiotactic form is where the substituents are located on alternate sides of the main chain. These forms are stereo-regular structures and exhibit strong tendancies to crystallize and as such, are essentially linear, head-to-tail polymers that are higher melting than amorphous type polymers. The atactic or amorphous polymer form is where substitution is completely random. The atactic polymers are also linear, head-to-tail polymers that are universally amorphous. The term "polypropylene polymers" is inclusive of all polymers derived from propylene whether essentially amorphous or essentially crystalline, including co-polymers, inclusive of block co-polymers, of propylene with one or more other monomers.
Polyolefins that are to be reinforced with glass fibers have been developed that are propylene acid compounds and that are blends of isotactic and amorphous polypropylene. Illustrative examples of the propylene acid compounds or acid-modified propylene polymers are U.S. Pat. Nos. 3,416,990 (Robinson); and 3,437,550 (Paul) and an article published by the Society of Automative Engineers entitled Properties of Reinforced Propylene/Acid Compounds by R. A. VanBrederode, R. A. Steinkamp, K. W. Bartz, K. L. Trachte and D. G. Stenmark No. 740292, February-March, 1974. Illustrative examples of the blends of isotactic and amorphous polypropylenes are presented in U.S. Pat. Nos. 3,073,790 and 3,483,276. In U.S. Pat. No. 3,073,790 (Bosoni) an aqueous dispersion of the isotactic polypropylene of any desired concentration even up to a concentration of 100 percent is made by stirring the polymer in the form of particles having a size between 0.1 and 20 microns into water at room temperature. In U.S. Pat. No. 3,483,276 (Mahlman) blends of propylene polymer and maleic anhydride-modified propylene polymers are prepared. The stereo-isomers either isotactic polypropylene or amorphous polypropylene can be blended with the maleic anhydride-modified propylene polymers. The modified polymers can be prepared by reacting maleic anhydride with any solid propylene polymer either crystalline or amorphous. When the blend of polypropylene and maleicanhydride modified polypropylene is used to coat metal, it can be applied either as an organosol or as a solution. The organosol is used in cases where either the modified or unmodified polymer is crystalline and thus insoluble at ordinary temperatures. If both polymers are amorphous, the solution method is employed.
Since the size composition containing polypropylene emulsion is an aqueous system, the use of organosol or even water dispersions of micronized polypropylene powder would not be recommended. Organic solvents are expensive, and create an explosion hazard if used in an area adjacent to high temperature and high voltage equipment. Additionally, micronized polyolefin dispersions tend to cream out (component of the dispersion separates out and rises to the surface) making the dispersion unusable. The use of such unstable water dispersions with an aqueous size system would provide application and process problems during fiber glass production. For these reasons it is desired to use a polyolefin binder material or finishing material as an aqueous emulsion. Because of the difficulties of obtaining an emulsion with isotactic polypropylene, the type of polypropylene typically used in commercial size compositions as discussed above was the amorphous polypropylene. Recently it has been suggested to use the isotactic polypropylene in the size composition U.S. Pat. No. 3,644,141 (Preston) in order to form the polypropylene emulsion, wherein the polypropylene was the isotactic polypropylene; and wherein the emulsion was prepared by first combining the polyolefin and water with an organo-silane and thereafter incorporating the combination into a water dispersible polyester resin. The water dispersible polyester resin particles acted as a carrier for the polyolefin organo silane material.
Since the polyolefin to be reinforced with glass fibers can be a blend of isotactic and amorphous polypropylene, there is a need to provide a better binder composition for use in the size composition for coating glass fibers to be used as reinforcement for blended or unblended polypropylenes. There is also a continuing need for improved binder composition for use in a size composition for application to glass fibers that are to be used as reinforcement in polyolefin materials. There is also a need in the technology of binder compositions to have a facile and safe aqueous emulsion of a binder composition which contains isotactic polypropylene to be incororated into size compositions for treating glass fibers to be used as reinforcement in polyolefins.